An integrated electronic circuit as a typical semiconductor is improved in the function by increasing the integration density. Thus, a manufacturing method of forming a conductive circuit in a vacuum with the sputtering or the vapor deposition has been adopted. Since it is a premise that the process is conducted in the vacuum, an apparatus thereof is expensive and a huge investment is required to shift a next generation of higher integration density. An enormous energy is also required in order to keep the vacuum condition. Therefore, a conductive nanoink necessary for forming the conductive circuit in an ink-jet type at normal temperature and at normal pressure.
Inorganic nanoparticles have been widely utilized in a conductive nanoink (e.g., see Patent Reference 1 and the like). Organic ligands protecting surfaces of the inorganic nanoparticles are indispensable in order to keep the inorganic nanoparticles staying stably in the nanoink. Since the organic ligand is electrically insulating, a thin coating film obtained by applying and drying nanoink of a nanoparticle solution is also electrically insulating. Conventionally, it was necessary to remove ligands by the post-treatment with chemicals and by firing at high temperature in order to convert it from electrically insulative to conductive. In such processing, there was limitation in selection of a substrate (e.g., see Non-patent Reference 1 and the like).
On the other hand, the present inventors investigated organic ligands and gold particles and presented a paper that characteristic optical properties were expressed with pi junction (e.g., see Non-patent Reference 2 and the like).